Background: The most common problem experienced by patients after Percutaneous Coronary Intervention (PCI) is back pain. After the procedure, patients are restricted to complete bed rest with no hip flexion for up to 10 hours, causing much discomfort, especially back pain. In some patients, anxiety arises due to limited movement, with the belief that movement might cause re-bleeding from the wound. To alleviate these problems, the "Siriraj Leg Lock" brace or SLL was initiated to confine the hip while allowing patients to freely move other parts of their body without complicating the wound. Hence, anxiety is relieved and mobility can lower the chance of getting back pain with more comfort. Objective: The aims of this experimental study were to investigate the effect and satisfaction of SLL on back pain in post-PCI patients, and to compare bleeding and/or hematoma occurrences at the site of incision between experimental and control groups. Material and Method: The randomized controlled trial (RCT) was conducted in 100 patients who underwent coronary angioplasty and/or stent placement interventions and received post procedural care at the intermediate cardiac care ward, Her Majesty Cardiac Center, from December 2006 to February 2007. The control group (49 patients) was to get standard care after the intervention, whereas the experimental group (51 patients) was fitted with the SLL device to allow free mobility right after the procedure. Results: Lower maximum back pain scores and mean back pain scores in the experimental group than in the control group, with statistical significance (p < 0.001). Back pain score reduced from the day of admission in the experimental group after applying SLL, but increased in the control group. The occurrence of hematoma in both groups was not significantly different (p = 0.114). The experimental group with the SLL could freely change positions from upright to decubitus without any effects to the wound, feeling more comfortable and experiencing less back pain. Patients' satisfaction towards the SLL from 1 to 5 scale was 4.3. The satisfaction was evident especially in patients who had previous PCI experience, and desired to ask for SLL application if a future procedure to be needed. Conclusion: Using SLL after sheath removal post PCI allows the patient to freely change position without any effects to the wound and reduces back pain with more patients' satisfaction.